If you overfill the system you would probably blow a seal somewhere. Remind me to tell you the story of how I blew both hoses clean off the compressor on my old car. It would be hard to overfill it with the hand-held can unless it was full already. How long where you pulling the trigger? Or did you use the machine? In theory you could let some gas out the low pressure port but of course that's illegal in CA. The good news is your ac is working and it will be 80F tomorrow
Normally I would say temperature switch but when I looked on realoem I did not see one in the system. It would be around the condenser or the receiver/dryer. Could be a short or relay relay issue for the fan too. The pressure switch determines whether the clutch engages and cycles the compressor (too low pressure = no, like if you have a leak) so maybe not an issue here. In some cars the aux fan comes on whenever the ac is on, is that the case for M5?